Is serum angiotensin-converting enzyme a suitable biomarker for differentiating idiopathic and demyelinating optic neuritis?

PURPOSE: The purpose of the study was to measure serum angiotensin-converting enzyme (ACE) in patients diagnosed with idiopathic and demyelinating optic neuritis (ON) as well as heathy individuals and assess its viability as a biomarker. METHODS: This clinical case-control study was conducted on patients diagnosed with acute ON as the case group and healthy controls aged between 18 and 50 years. Based on findings from systemic and neurological evaluation, the study group was divided into: Idiopathic ON and demyelinating ON (including multiple sclerosis [MS], neuromyelitis optica [NMO], and clinically isolated syndrome [CIS]) subgroups. Serum ACE levels were measured using enzyme-linked immunosorbent assay and compared between groups. RESULTS: Fifty-one patients with acute ON (78.4% female, mean age 29.8 ± 8.4 years) and 51 controls (78.4% female, mean age 29.9 ± 6.9 years) were enrolled in this study. In the case group, 29 patients were diagnosed with idiopathic ON (56.9%), and 22 patients with demyelinating types of ON (43.1%) (MS-ON, n = 16; NMO-ON, n = 3; and CIS, n = 3). The median serum ACE levels were 33.50 U/L (range: 29.40-46.20), and 34.25 U/L (range: 29.30-46.10) for patients diagnosed with idiopathic ON and demyelinating ON, respectively (P > 0.99). The mean serum ACE level for healthy individuals was 26.2 U/L (range: 24.80-20.50), and compared to other groups, it was significantly different (P < 0.001). Abnormal levels of serum ACE (defined as a serum ACE >65 U/L) were measured in 3 (10.3%) patients with idiopathic ON and 2 (9.1%) patients with the demyelinating ON (P > 0.99). CONCLUSION: Our findings did not exhibit a significant difference in terms of serum ACE level between patients diagnosed with idiopathic ON and demyelinating ON. However, serum ACE level in both groups is significantly higher compared to healthy subjects.